Have you accidentally over-chlorinated your pool?
An elevated chlorine level isn’t usually a serious problem, but it can lead to some complications with the balance of your water. It also makes for a less enjoyable swim.
Not to worry, we’re going to cover the 4 best methods to lower your chlorine level, starting from best to worst.
Quick answer: Aside from waiting for your chlorine level to fall naturally (slow), adding a chlorine neutralizer like sodium thiosulfate to your water is easily the fastest and most controlled way to lower the chlorine level.
How High is Too High?
The recommended free chlorine level for most pools is somewhere between 2 and 3 parts per million (ppm), but it’s actually safe to swim at levels much higher than this.
The exact limit? Well, it depends.
Your cyanuric acid level (CYA) plays an important role here. The more of it you have in your water, the higher this limit will be. This is because CYA effectively weakens your chlorine after bonding with it.
Here’s a handy table for safe swimming limits:
|Cyanuric acid level (ppm)||Max. free chlorine level (ppm)|
On that note, you won’t have much wiggle room if your water exceeds the recommended chlorine level while having little to no cyanuric acid in your water, so always err on the side of caution.
4 Ways to Lower Your Chlorine Level (Best to Worst)
As promised, let’s break down the best ways to reduce your chlorine level:
1. Wait for It to Drop Naturally
If you’re in no hurry to use the pool, waiting it out is the easiest and most cost-effective approach to lowering your free chlorine level.
Without use, most pools naturally lose free chlorine at an average daily rate of around 2 to 3 ppm, though this is influenced by things like water temperature, UV exposure, and the cyanuric acid level.
Assuming your chlorine level isn’t too far above 10 parts per million, it’ll take anywhere from a few days to a week for it to drop back into the appropriate range. If your chlorine is any higher than that you’ll probably want to take a different approach.
Just be sure to remove all chlorine sources from your pool. Turn off the chlorinator or saltwater chlorine generator, and take any chlorine tablets out of the pool skimmer or floater. You’ll also want to leave your pool cover off during this time, at least during the day.
- Requires little to no effort
- Doesn’t require any chemicals
- Doesn’t cost anything
- It’s not a quick fix
- Even slower if your pool is in the shade
2. Use a Chlorine Neutralizer
If your chlorine level is really high or you just don’t have the luxury of time, consider adding a chlorine neutralizer to your water.
This is exactly what it sounds like; a chemical that reacts with chlorine, breaking it down and effectively rendering it useless. What’s more, commonly used neutralizers work in as little as a few hours.
Most pool owners use sodium thiosulfate, sodium sulfite, or sodium metabisulfite. They’re all just as effective as one another and none will drastically impact the rest of your water chemistry, so buy whatever is easiest or cheapest in your area.
Here’s how much you’ll need to reduce the free chlorine level by 1 ppm:
|Chlorine neutralizer||Amount needed (weight)|
|Sodium thiosulfate||2.6 oz per 10,000 gallons|
|Sodium sulfite||2.4 oz per 10,000 gallons|
|Sodium metabisulfite||1.5 oz per 10,000 gallons|
Don’t worry, you don’t have to run the math.
We created a ‘chlorine neutralizer dosage’ calculator so you can adjust the values yourself and get the exact dosage for each type.
Take it away:
- Allows for precise reduction of chlorine
- Provides results in a matter of hours
- No adverse effects on your water chemistry
- It costs money
- May not be readily available in your area
3. Put the Chlorine to Work
Chlorine gets used up as it fights off contaminants in the water, which is why it constantly needs topping up under normal circumstances.
But you can also use this to your advantage. If your chlorine level is only a little too high, you can help it back down by simply giving it more “stuff” to sanitize.
The easiest way to go about introducing more contaminants to your pool is to go for a swim. Natural body oils like sweat and saliva have a measurable impact on your chlorine level, especially if you can get more bodies involved.
There is a catch, however.
The more your chlorine has to work, the more combined chlorine (chloramines) builds up in your water. This leads to a whole new set of problems that can only be fixed by shocking your pool; ultimately forcing you to add even more chlorine to the mix.
As a result, you should only ever use this approach to make minor reductions in your free chlorine level.
- Gives an excuse to throw a pool party
- Doesn’t require any chemicals
- Doesn’t cost anything
- Not very precise
- Increases your combined chlorine
4. Drain and Replace Some Water
The least desirable option has to be draining and refilling.
While diluting a chlorine-heavy pool with fresh water offers a relatively quick turnaround, it doesn’t come without heavy considerations.
The first is volume, as you’ll need to drain a significant amount of water to make any meaningful impact on your chlorine level.
For example, just halving your chlorine level requires that you empty half of the pool water. Even for a smaller pool, that’s a lot of treated water to move before even thinking about the environmental impact or local regulations.
Then there’s the cost aspect.
As well as replacing the water you took out, you’ll need to replace the other chemicals you lost during this process to rebalance your water. There’s also the potential risk of damaging your pool structure – which, unfortunately, always comes with draining a swimming pool.
A partial drain and refill might not be too much hassle if you’re correcting slightly over-chlorinated water, but if it’s only slight, you’re almost always going to be better off just waiting it out.
- Potentially a fast solution
- May require rebalancing the water
- Loss of other dissolved chemicals in the process
- Replacing the water likely isn’t free
- Not ideal for larger pools
How to Prevent a High Chlorine Level
Let’s finish up with some practical tips on how to prevent your chlorine level running away from you in future.
- Proper testing. Always get an accurate read on your chlorine level before adding more to your water. Consider investing in a liquid testing kit for the most reliable results.
- Monitor your pH level. Chlorine works best at a lower pH level, so letting your pH drift too high could result in having to add more chlorine. The sweet spot for pH is between 7.2 to 7.8.
- Monitor your CYA. Cyanuric acid (CYA) will prevent the sun from burning through your chlorine, but too much will also weaken your chlorine to a point where an extreme amount is needed to maintain proper sanitation.
- Manual chlorination. Chlorine tablets can be helpful when you need a set-and-forget solution, but manually adding chlorine (such as liquid chlorine) will give you the most control over your free chlorine level.
- Automatic chlorination. Alternatively, an automatic chlorine feeder controls when and how much chlorine gets into your water, so you never have to worry about accidentally adding too much to your pool.
The Bottom Line
Despite having a number of methods at your disposal, the best thing you can do to fix a high chlorine level is to just let nature run its course.
If you do need a quick fix, however, adding a chlorine neutralizer (for big adjustments) or simply swimming in your pool (for small adjustments) will get you results in hours as opposed to days.
Don’t bother with draining unless you have other issues with your water that could also be resolved through draining and refilling.